1. Technical Field
The present disclosure relates generally to printed circuit boards and, more particularly, to a stepped printed circuit board for use with snap-domes in medical devices.
2. Background of Related Art
A wide variety of electrosurgical devices have been developed in the past for use by surgeons during various operations. For example, pulse-like electrosurgical devices have been used for a variety of operations for cauterizing and coagulating tissue during surgery. In addition, apparatii using high frequency or RF pulses (i.e., radio frequency pulses) have been employed for cutting tissue utilizing exposed electrodes having various geometries, e.g., loop wires, needle electrodes, ball-like electrodes, blade-like electrodes and the like. Early electrosurgical devices generally required actuation via foot switches or manual switches which were remotely located relative to the surgical site often requiring the surgeon to seek assistance during the operation.
In order to provide the surgeon with more direct control of the instrument, devices have been developed enabling electrosurgical mode selection and electrosurgical activation of the signals supplied to the electrode (for example, a continuous A.C. signal for cutting or a pulse A.C. signal for coagulating), switches are mounted on the instrument body which allow the surgeon to selectively activate and control the energy emission from the electrosurgical generator. In this manner, the switches permit the surgeon to select varying modes of operation of the same instrument during surgery. The switches are typically sealed to prevent fluids or tissue from contaminating or affecting the interior electronics of the instrument to assure proper operation of concomitant precision and safety during use.
A typical switch for electrosurgical pencil includes a tactile or audible feedback membrane switch, wherein one or both of the switch contacts is/are incorporated into an insulative substrate having a film base on a circuit board panel. The under side of a flexible upper membrane, which overlies the substrate and is spaced apart from the contacts thereon includes a conductive member which may be the other of the switch contacts or a conductive bridge, either of which is adapted to close the contacts upon depression of the flexible membrane.
The problem with tactile or audible feedback membrane switches is that their operation requires a very light force, and a very small deflection in order to complete and close the contact. Thus, without any feedback (i.e., visual, tactile or audible) many operators have difficulty sensing switch closure.
One solution to the problem of tactile feedback or feel has been the introduction of a resilient metal dome which is flexible and which has a certain xe2x80x9csnapxe2x80x9d when depressed. In use, the marginal edge of the dome is in electrical contact with a first terminal carried by an insulating substrate, while the center of the dome overlies another terminal also carried by the substrate. Upon depression, the central region of the dome contacts the central terminal completing the electrical connection between the two terminals and activating the switch. Upon connection, a simultaneous xe2x80x9csnapxe2x80x9d is either felt in the surgeon""s finger or heard.
Other prior art designs have used an embossed plastic bubble rather than a metal dome which is overlaid on the membrane switch or on a separate layer between the membrane and the overlay. One drawback to the plastic bubble concept is that the plastic bubble often produces undesirable tactile characteristics because it does not uniformly deflect over its entire area. Since the bubble does not deform consistently toward the center, an undesirable xe2x80x9cteasingxe2x80x9d effect may occur. Switch teasing is undesirable because the operator may receive an acceptable tactile feel response, yet the switch may not close properly or consistently.
Another drawback in the use of the plastic bubble concept is the lack of effective tactile feedback. In other words, it may be difficult to sense (tactically) actual electrical contact with the underlying printed circuit board upon depression of the plastic dome. Moreover, current printed circuit board designs utilize domes having a single plane deposition thickness on the board which further limits overall tactile feedback.
While there have been many attempts to produce suitable and effective electrosurgical devices with finger-operated tactile feedback switches, there exists a need to develop a feedback switch and circuit board arrangement which, when depressed, effectively completes the electrical circuit and provides reliable sensory feedback to the surgeon during use.
The present disclosure is directed to stepped printed circuit board snap-domes for use in medical devices in order to improve the tactile feedback to a surgeon operating a surgical instrument on which the snap-dome is mounted.
In accordance with one aspect of the present disclosure a tactile switch assembly for use with a surgical instrument includes a substrate, an inner terminal disposed on an upper surface of the substrate and having a first height, an outer terminal disposed on the upper surface of the substrate and substantially surrounding the inner terminal and having a second height which is greater than the height of the inner terminal and a snap-dome secured to the substrate and having a periphery engaged to and in electrical communication with the outer terminal. The snap-dome is depressible through a range wherein, upon inversion of the snap-dome, an apex of the snap dome electrically connect the inner and outer terminals.
Preferably, the snap-dome is connected to the outer terminal at a plurality of contact points. It is envisioned that the outer terminal is substantially ring-like and the outer peripheral edge of the snap-dome is contiguous therewith.
Preferably, the tactile switch assembly further includes an electrosurgical regulator which regulates the amount of electrosurgical energy transmitted upon activation of the tactile switch.
In another aspect of the present disclosure, the tactile switch assembly includes a substrate made of a non-conductive material, a first inner terminal, a second inner terminal and an outer terminal. The first inner terminal is disposed on an upper surface of the substrate and is made from a conductive material defining a first height. The second inner terminal is disposed on the upper surface of the substrate and is internal of the first inner terminal. The second inner terminal is made from a conductive material and defines a second height which is less than the height of the first inner terminal. The outer terminal is disposed on the upper surface of the substrate and substantially surrounds the first inner terminal. The outer terminal is made from a conductive material and defines a third height which is greater than the first height of the first inner terminal.
The tactile switch assembly according to the present aspect of the disclosure further includes a snap-dome secured to the substrate and having a periphery engaged to and in electrical communication with the outer terminal. The snap-dome is depressible through a range wherein, upon depression of the snap-dome, an apex of the snap-dome electrically interconnects the first inner terminal and the outer terminal. Moreover, upon continued depression the apex of the snap-dome electrically interconnects the second inner terminal and the outer terminal.
In yet another aspect there is disclosed a printed circuit board for use with a snap-dome switch of a medical instrument. The printed circuit includes a non-conductive substrate defining an upper surface, a first conductive terminal disposed on the upper surface of the substrate, wherein the first conductive terminal defines a first height, and a second conductive terminal disposed on the upper surface of the substrate, wherein the second conductive terminal defines a second height which is greater than the height of the first conductive terminal. Preferably, the second conductive terminal is generally concentrically spaced from the first conductive terminal.
It is envisioned that the snap-dome is contiguous with the second conductive terminal. Preferably, the snap-dome is depressible through a range wherein upon inversion of the snap-dome an apex of the snap-dome electrically connects the first and second terminals.
In an alternative embodiment, the tactile switch assembly includes a substrate, a plurality of contact pads disposed on an upper surface of the substrate, a turntable rotatably mounted on the upper surface of the substrate, an inner terminal disposed on an upper surface of the turntable, an outer terminal disposed on the upper surface of the substrate and substantially surrounding the inner terminal, the outer terminal having an electrical lead extending therefrom and being electrically contactable with a selected one of the plurality of contact pads and a snap-dome secured to the turntable and having a periphery engaged to and in electrical communication with the outer terminal.
Preferably, the substrate and the turntable are made from non-conductive materials while each contact pad, the inner terminal and the outer terminal are made from conductive materials. Preferably, each contact pad is electrically connected to an electrosurgical energy source.
These and other objects will be more clearly illustrated :below by the description of the drawings and the detailed description of the preferred embodiments.